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MK 4 Golf woes
corrado vr6 - 27/6/21 at 08:42 AM

Morning all,

I’m posting on here as unfortunately I don’t get any help/responses on the VW or TDI groups.
I have an ongoing issue with my MK4 golf PD150 ARL.

Some months ago I had the engine rebuilt (done for the love)

Since the engine went in it starts perfectly but just won’t rev past 2000rpm.

I removed the exhaust down pipe once and it did rev up and everything sounded great thinking I had a blocked cat, left the car over night with the exhaust still off and the next start up it still wouldn’t rev.

It’s not like its limited at 2000rpm but as if it’s starved of fuel or air, something just isn’t right!

The only fault code that keeps showing up is the engine speed sensor or crank sensor intermittent. I have changed the sensor for a non gen one (Febi, genuine sensor is £80!) and the car mostly wouldn’t start. When it did start it would rev up on its own but with no throttle response, or tacho. The only way to stop it was to turn the ignition off. In the end it became so hard to start I put the old genuine sensor back in, it now starts every time first turn of the key but won’t rev up and fault code still gets logged.

I know it can rev up cleanly as it has done it 3 or 4 times now but just cannot replicate it to know what it is that’s at fault! Thinking it must be electrical or sensor as mechanical things don’t really change that one point it can work and then another it won’t.


Parts that have been replaced

- injectors for second hand set
- injector loom
- in tank lift pump
- crank sensor this has now been swapped back again to gen sensor
- MAF sensor
- tandem pump swapped briefly

[Edited on 27/6/21 by corrado vr6]

gremlin1234 - 27/6/21 at 09:29 AM

I would check the alignment / mounting for the crank position sensor.
it could have been knocked/ bent when engine work was done

[Edited on 27/6/21 by gremlin1234]

steve m - 27/6/21 at 03:40 PM

Cam timing wrong?

Any normal engine will run, with a cam sprocket tooth one position out, and that will result in an engine that will not rev, bit will start

[Edited on 27/6/21 by steve m]

adithorp - 27/6/21 at 05:27 PM

Put a genuine (or Bosch) crank sensor in it. All other aftermarket ones are shite ...OK, sometimes you get a good one but it's rare and really not worth the effort. The only times I use them is when I can't get a genuine one and the customer insists they need the car back and won't wait. I tell them I'll see them again in a few days and I'm usually right.
Once you've sorted that it'll either be right or any second fault will be easier to track down. Difficult to understand/trace faults are often actually two (or more) faults.

ReMan - 27/6/21 at 06:18 PM

Sure I read on a another forum that these are sensitive to correct sensors crank/abs etc?
So could you borrow another gen one?

corrado vr6 - 27/6/21 at 07:24 PM

Hi, thanks all

I have tried two genuine sensors that were both working fine in two other engines.

It seems to be slightly intermittent as it has at times suddenly revved up, once when banging on the fuel tank thinking it was a lift pump issue and the other few times were when I removed the exhaust down pipe.

I forgot to mention I did have an ESP light constantly on and the diagnostics said the ESP sensor was defective. I have since changed the ESP sensor which has turned the light off but now the ABS light is on, however this model does need to carry out a test by doing 20 mph and doing left and right turns to set itself up, however I can’t do 20mph without it bucking and hesitating, so I don’t think the ABS light is my issue.

I have read today that the crank shaft sensor wiring is shielded so guessing if that’s damaged in any way it’ll get interference

ak - 27/6/21 at 08:59 PM

I had a very similar issue on my BMW e46 330Ci - fault codes pointed to crank sensor. Replaced it with a rather expensive BMW sensor, but no improvement. Symptoms were intermittent - occasionally it'd seem to be fixed for 30 miles or so, then extremely rough running and became undriveable. Extremely annoying as I lost all confidence in it! Eventually gave it to an independent BMW specialist to look at.

Turned out to be a very slight coolant leak from the thermostat housing causing coolant to be pumped up a wiring loom via capillary action. This led to corrosion on the crank position sensor pins on the ECU. Pins were cleaned up and terminals soldered on to re-form the connection. And of course, the thermostat housing was replaced to fix the source of the problem.

Probably would have taken me another painful few days/weeks of diagnosis to find that issue myself!

So, maybe check your ECU inputs wiring?

[Edited on 27/6/21 by ak]

jollygreengiant - 28/6/21 at 08:44 AM

It might sound like a very silly one, but, HAVE you checked the fuel filter(s) (some times they might have two, one JUST after the tank and then the MAIN one in the engine bay)
I was using a Peugeot 406 at one time, then every now and then it would switch on the EML and not rev above 2000. This fault turned out to be a shed load of crud in the fuel system, particularly in the main big filter. slowly the flow of fuel would agitate it and it would be held onto the filter material until there was enough coverage to restrict the flow, which increased the flow and pressure until there was insufficient fuel flow for anything above 2000 rpm. take it to the garage for diagnostic they would start it after being parked for a while and surprise surprise it would be fine until the next time it happened. Had to take the fuel filter body off completely, take it apart, THOROUGHLY clean it internally, clean fit new filter, flush the bleed off/re-circulation pipes and refit filter/bleed system. It ran as good as gold and sweet as a nut after that.
Just a thought. HTH's

gremlin1234 - 28/6/21 at 12:24 PM

quote:
Originally posted by jollygreengiant
It might sound like a very silly one, but, HAVE you checked the fuel filter(s) (some times they might have two, one JUST after the tank and then the MAIN one in the engine bay)
I was using a Peugeot 406 at one time, then every now and then it would switch on the EML and not rev above 2000. This fault turned out to be a shed load of crud in the fuel system, particularly in the main big filter. slowly the flow of fuel would agitate it and it would be held onto the filter material until there was enough coverage to restrict the flow, which increased the flow and pressure until there was insufficient fuel flow for anything above 2000 rpm. take it to the garage for diagnostic they would start it after being parked for a while and surprise surprise it would be fine until the next time it happened. Had to take the fuel filter body off completely, take it apart, THOROUGHLY clean it internally, clean fit new filter, flush the bleed off/re-circulation pipes and refit filter/bleed system. It ran as good as gold and sweet as a nut after that.
Just a thought. HTH's


no that does not sound silly, its certainly a possibility.
also in the same vein, check the tank breather. (or see if it runs better without the fuel filler cap in place)

nick205 - 28/6/21 at 01:53 PM

quote:
Originally posted by jollygreengiant
It might sound like a very silly one, but, HAVE you checked the fuel filter(s) (some times they might have two, one JUST after the tank and then the MAIN one in the engine bay)
I was using a Peugeot 406 at one time, then every now and then it would switch on the EML and not rev above 2000. This fault turned out to be a shed load of crud in the fuel system, particularly in the main big filter. slowly the flow of fuel would agitate it and it would be held onto the filter material until there was enough coverage to restrict the flow, which increased the flow and pressure until there was insufficient fuel flow for anything above 2000 rpm. take it to the garage for diagnostic they would start it after being parked for a while and surprise surprise it would be fine until the next time it happened. Had to take the fuel filter body off completely, take it apart, THOROUGHLY clean it internally, clean fit new filter, flush the bleed off/re-circulation pipes and refit filter/bleed system. It ran as good as gold and sweet as a nut after that.
Just a thought. HTH's




This doesn't sound silly at all - very sensible in fact!

I had a Seat Leon Cupra TDI (PD150 engine) and have had a number of diesels since. Annual fuel filter replacement is cheap easy and does no harm. It allows the fuel to flow cleaner and free to the engine.

When you replace the filter element it's best practice to fill the filter housing (vertical metal can) with clean new diesel before refitting the lid. This avoids air locks in the fuel system and ensures an easier engine start after the work has been done. I've done the job myself a number of times on a number of VW and Seat vehicles.

It also seems to be a service task that most garages completey overlook - an OEM filter element costs less then £10 and the job takes 15 minutes. You can do it while the engine oil's draing for the oil change.

rusty nuts - 28/6/21 at 07:35 PM

Had similar problems with a Golf that turned out to be incorrect valve timing but I can’t remember which engine code it was, there are at least two different crankshaft setting tools for VW Diesel engines if not more. Might also be worth checking the brake light switch as they can and do cause problems cutting the engine revs as if the bakes have been applied . Flybywire throttle pedals can have problems with the potentiometer side of things